Organic light-emitting display device

ABSTRACT

A display device includes a switching transistor, a driving transistor, a storage capacitor connected to the switching and driving transistors, and an organic light-emitting diode connected to the driving transistor. The driving transistor is connected to the switching transistor. The driving transistor includes a semiconductor layer having a channel region, first doped regions at sides of the channel region, and second doped regions doped with impurities of a concentration greater than the first doped regions. A first electrode layer is over an insulating layer, which covers the semiconductor layer. The electrode layer includes convex portions extending toward the first doped regions and covering an end of the channel region. At least one of the convex portions has a width greater than or equal to a width of the end of the channel region.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2016-0036953, filed on Mar. 28, 2016,and entitled, “Organic Light-Emitting Display Device,” is incorporatedby reference herein in its entirety.

BACKGROUND

1. Field

One or more embodiments relate to an organic light-emitting displaydevice.

2. Description of the Related Art

An organic light-emitting display device includes a plurality of pixelsthat emit light to form an image. Each pixel includes a pixel circuit,an organic light-emitting diode, and an organic emission layer betweentwo electrodes. The pixel circuit includes thin film transistors and acapacitor for driving the organic light-emitting diode. The transistorsinclude a switching transistor and a driving transistor. In operation,electron and holes injected from the electrodes recombine in the organicemission layer to form excitons. Light is emitted when the excitonschange state and release energy.

The gray scale value of light emitted from each pixel may be determinedby adjusting the magnitude of a gate voltage Vgs of the drivingtransistor. The driving range of the driving transistor is based on thegate voltage Vgs, which is related to the channel length of asemiconductor layer of the driving transistor. The semiconductor layermay include polycrystalline silicon or amorphous silicon. Since theelectron mobility of polycrystalline silicon is greater than that ofamorphous silicon, polycrystalline silicon is generally used.

A polycrystalline silicon transistor has an off-current greater thanthat of an amorphous silicon transistor. In an attempt to compensate forthe greater off-current of the polycrystalline silicon transistor, alightly doped region may be arranged between heavily doped source anddrain regions and a channel region of the polycrystalline silicontransistor.

SUMMARY

In accordance with one or more embodiments, an organic light-emittingdisplay device includes a switching thin film transistor; a driving thinfilm transistor electrically connected to the switching thin filmtransistor, the driving thin film transistor including a drivingsemiconductor layer which includes a driving channel region, first dopedregions at sides of the driving channel region, and second doped regionsdoped with impurities of a concentration greater than the first dopedregions; a storage capacitor electrically connected to the switchingthin film transistor and the driving thin film transistor; an organiclight-emitting diode electrically connected to the driving thin filmtransistor; a first insulating layer covering the driving semiconductorlayer; and a first electrode layer over the first insulating layer,wherein the first electrode layer includes convex portions extendingtoward each of the first doped regions and covering an end of thedriving channel region and wherein at least one of the convex portionshas a first width greater than or equal to a width of the end of thedriving channel region.

The first width may be less than a second width of the first electrodelayer in a same width direction as the first width at a point, and thepoint may be a midpoint of a channel length of the driving channelregion. The driving channel region may be curved. The drivingsemiconductor layer may include a plurality of curved portions.

The display device may include a second insulating layer overlapping thefirst electrode layer, a second electrode layer overlapping the firstelectrode layer, and the second insulating layer is between the firstand second electrode layers. The first electrode layer may serve as adriving gate electrode of the driving thin film transistor and as aplate of the storage capacitor. The first electrode layer may include asecond convex portion adjacent to at least one of the convex portions,and the at least one convex portion may be spaced from the second convexportion. The second convex portion may extend in a same direction as anextension direction of the at least one convex portion. The at least oneconvex portion may be spaced apart from the second convex portion in awidth direction of the convex portion.

The switching thin film transistor may include a switching channelregion, third doped regions at sides of the switching channel region,and fourth doped regions doped with impurities of a concentrationgreater than the third doped regions. The first doped regions and thethird doped regions may include a same material. The length of theswitching channel region is less than a length of the driving channelregion. The first doped regions may not overlap the convex portions.

In accordance with one or more other embodiments, a semiconductor deviceincludes a first transistor including a semiconductor layer, thesemiconductor layer includes first doped regions, a channel regionbetween the first doped regions, and second doped regions doped withimpurities of a greater concentration than the first doped regions; aninsulating layer covering the semiconductor layer; and an electrodelayer over the insulating layer, wherein the electrode layer includesone or more convex portions extending toward the first doped regions,the one or more convex portions covering an end of the channel region,and wherein at least one of the convex portions has a first widthgreater than or equal to a width of the end of the channel region.

The first width may be less than a second width of the electrode layerin a same width direction as the first width at a point, and the pointmay be a midpoint of a channel length of the driving channel region. Thechannel region may be curved. The semiconductor layer may include aplurality of curved portions. The semiconductor device may include astorage capacitor connected to the transistor, wherein the electrodelayer serves as a gate electrode of the transistor and a plate of thestorage capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates an embodiment of an organic light-emitting displaydevice;

FIG. 2 illustrates an embodiment of a pixel;

FIG. 3 illustrates a layout view of the pixel;

FIG. 4 illustrates cross-sectional views of the pixel;

FIG. 5 illustrates a plan view of a portion V in FIG. 3;

FIGS. 6a-6c illustrate embodiments of a method for manufacturing adriving thin film transistor and a switching thin film transistor;

FIG. 7 illustrates another embodiment of a driving thin film transistor;

FIG. 8 illustrates another embodiment of a driving thin film transistor;

FIG. 9 illustrates another embodiment of a driving thin film transistor;

FIG. 10 illustrates another embodiment of a driving thin filmtransistor;

FIG. 11 illustrates a driving thin film transistor and a switching thinfilm transistor according to a comparative example; and

FIGS. 12a-12c illustrate embodiments of a method for manufacturing thedriving thin film transistor and the switching thin film transistor ofFIG. 11.

DETAILED DESCRIPTION

Example embodiments are described with reference to the drawings;however, they may be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will convey exemplary implementations to those skilled inthe art. The embodiments (or portions thereof) may be combined to formadditional embodiments.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

When an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the anotherelement or be indirectly connected or coupled to the another elementwith one or more intervening elements interposed therebetween. Inaddition, when an element is referred to as “including” a component,this indicates that the element may further include another componentinstead of excluding another component unless there is differentdisclosure.

FIG. 1 illustrates an embodiment of an organic light-emitting displaydevice which includes a display area DA (active area) and a non-displayarea NDA (dead area). The display area DA includes a plurality of pixelsP emitting light. Each pixel P emits light of one of a plurality ofcolors, e.g., red, green, or blue. The non-display area NDA may surroundthe display area DA and include drivers such as a scan driver and a datadriver for transferring a predetermined signal to the pixels P in thedisplay area DA.

FIG. 2 illustrates an embodiment of a pixel P, which may berepresentative of the pixels in the organic light-emitting displaydevices of FIG. 1. Referring to FIG. 2, each pixel P includes a pixelcircuit for driving an organic light-emitting diode (OLED). The pixelcircuit may include at least two thin film transistors and at least onestorage capacitor.

Referring to FIG. 2, the transistors may include a driving TFT T1, aswitching TFT T2, a compensation TFT T3, an initialization TFT T4, anoperation control TFT T5, and an emission control TFT T6. The drivingTFT T1 includes a gate electrode connected to one of electrodes of astorage capacitor Cst, a source electrode connected to a driving voltageline 172 via the operation control TFT T5, and a drain electrode iselectrically connected to an anode of the OLED via the emission controlTFT T6. The driving TFT T1 receives a data signal Dm and supplies adriving current Id to the OLED based on a switching operation of theswitching TFT T2.

The switching TFT T2 includes a gate electrode connected to a scan line121, a source electrode connected to a data line 171, and a drainelectrode connected to the source electrode of the driving TFT T1 andsimultaneously connected to the driving voltage line 172 via theoperation control TFT T5. The switching TFT T2 is turned on based on ascan signal Sn received via the scan line 121 and performs a switchingoperation of transferring a data signal Dm from the data line 171 to thesource electrode of the driving TFT T1.

The compensation TFT T3 includes a gate electrode connected to the scanline 121, a source electrode connected to the drain electrode of thedriving TFT T1 and simultaneously connected to the anode of the OLED viathe emission control TFT T6, and a drain electrode connected to one ofthe electrodes of the storage capacitor Cst, a drain electrode of theinitialization TFT T4, and the gate electrode of the driving TFT T1simultaneously. The compensation TFT T3 is turned on based on a scansignal Sn transferred via the scan line 121 and compensates for athreshold voltage of the driving TFT T1 by connecting the gate electrodeto the drain electrode of the driving TFT T1, and thus connectingdiode-connecting the driving TFT T1.

The initialization TFT T4 includes a gate electrode connected to aprevious scan line 122, a source electrode connected to theinitialization voltage line 124, and a drain electrode connected to oneend Cst1 of the storage capacitor Cst, the drain electrode of thecompensation TFT T3, and the gate electrode of the driving TFT T1simultaneously. The initialization TFT T4 is turned on based on aprevious scan signal Sn-1 transferred via the previous scan line 122 andperforms an initialization operation of initializing the voltage of thegate electrode of the driving TFT T1, by transferring an initializationvoltage Vint to the gate electrode of the driving TFT T1.

The operation control TFT T5 includes a gate electrode connected to anemission control line 123, a source electrode of the operation controlTFT T5 is connected to the driving voltage line 172, and a drainelectrode of the operation control TFT T5 is connected to the sourceelectrode of the driving TFT T1 and the drain electrode of the switchingTFT T2 simultaneously. The operation control TFT T5 is between thedriving voltage line 172 and the driving TFT T1. The operation controlTFT T5 is turned on based on an emission control signal En from theemission control line 123 and transfers a driving voltage ELVDD to thedriving TFT T1.

The emission control TFT T6 includes a gate electrode connected to theemission control line 123, a source electrode of the emission controlTFT T6 is connected to the drain electrode of the driving TFT T1 and thesource electrode of the compensation TFT T3 simultaneously, and a drainelectrode of the emission control TFT T6 is electrically connected tothe anode of the OLED. The emission control TFT T6 is between thedriving TFT T1 and the OLED. The emission control TFT T6 is turned onbased on an emission control signal En from the emission control line123 and transfers the driving voltage ELVDD from the driving TFT T1 tothe OLED.

In the embodiment of FIG. 2, each pixel P includes six TFTs. In oneembodiment, each pixel P may include a different number (e.g., seven) ofTFTs depending, for example, on the design of the pixel circuit.

The other electrode of storage capacitor Cst is connected to the drivingvoltage line 172. A cathode of the OLED is connected to a common voltageELVSS. The OLED emits light based on driving current Id from the drivingTFT T1 to display an image.

During an initialization period, when a previous scan signal Sn-1 issupplied from the previous scan line 122, the initialization TFT T4 isturned on based on the previous scan signal Sn-1 and the driving TFT T1is initialized by the initialization voltage Vint from theinitialization voltage line 124.

During a data programming period, when a scan signal Sn is supplied viathe scan line 121, the switching TFT T2 and the compensation TFT T3 areturned on based on the scan signal Sn. The driving TFT T1 is thendiode-connected and forward-biased by the turned-on compensation TFT T3.

Then, a compensation voltage is applied to the driving gate electrode ofthe driving TFT T1. The compensation voltage Dm+Vth (Vth has a (−)value) is reduced by a threshold voltage Vth of the driving TFT T1 froma data signal Din supplied from the data line 171. The driving voltageELVDD and the compensation voltage Dm+Vth are applied to ends of thestorage capacitor Cst, and a charge corresponding to a voltagedifference between the ends is stored in the storage capacitor Cst.

During an emission period, operation control TFT T5 and emission controlTFT T6 are turned on based on an emission control signal En supplied viathe emission control line 123. A driving current Id is generated basedon the voltage difference between a voltage of the gate electrode of thedriving TFT T1 and the driving voltage ELVDD. The driving current Id issupplied to the OLED via emission control TFT T6.

FIG. 3 illustrates a layout view of a pixel of an organic light-emittingdisplay device, which pixel may correspond to pixel P. FIG. 4illustrates a cross-sectional view of the pixel P taken along linesIVa-IVa and IVb-IVb of FIG. 3.

Referring to FIG. 3, the pixel P includes the scan line 121, theprevious scan line 122, the emission control line 123, and the initialvoltage line 124 extending in an X-direction. The data line 171 and thedriving voltage line 172 extend in a Y-direction crossing theX-direction. The pixel P includes the driving TFT T1, the switching TFTT2, the compensation TFT T3, the initialization TFT T4, the operationcontrol TFT T5, the emission control TFT T6, and the storage capacitorCst connected to these lines. Regarding the structure of a pixel P, thedriving TFT T1, the switching TFT T2, and the storage capacitor Cst aremainly described according to a stacking order. The structure of theother TFTs may be similar to a stacking structure of the switching TFT.

Referring to FIGS. 3 and 4, a buffer layer 101 is on a substrate 110,which may include a glass material, a metallic material, or a plasticmaterial such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyimide, etc. The buffer layer 101 may include anoxide layer such as SiOx and/or a nitride layer such as SiNx.

The semiconductor layer 131 is on the buffer layer 101. Thesemiconductor layer 131 may include polycrystalline silicon, a channelregion not doped with impurities, and a source region and a drain regiondoped with impurities in different sides of the channel region. Thesemiconductor layer 131 may include a lightly doped region doped withimpurities of a relatively low concentration between the channel regionand the drain region. In another embodiment, the impurities may bedifferent depending, for example, on the kind of TFT. Examples of theimpurities include N-type impurities or P-type impurities.

The semiconductor layer 131 includes a driving semiconductor layer 131 aof the driving TFT T1 and a switching semiconductor layer 131 b of theswitching TFT T2. The driving semiconductor layer 131 a is connected toswitching semiconductor layer 131 b.

The driving semiconductor layer 131 a includes a driving channel region131 a 1 and first doped regions 141 a and 142 a including firstimpurities. The first doped regions 141 a and 142 a are at differentsides of the driving channel region 131 a 1. Second doped regions 176 aand 177 a include second impurities with a greater concentration thanthe first impurities. The second doped regions 176 a and 177 a are atdifferent sides of the driving channel region 131 a 1, and the firstdoped regions 141 a and 142 a are therebetween. The second doped regions176 a and 177 a respectively correspond to a source region and a drainregion. The source region and the drain region respectively correspondto a source electrode and a drain electrode.

The switching semiconductor layer 131 b includes a switching channelregion 131 b 1, third doped regions 141 b and 142 b including thirdimpurities, the third doped regions 141 b and 142 b at different sidesof the switching channel region 131 b 1, and fourth doped regions 176 band 177 b including fourth impurities with a greater concentration thanthe third impurities. The fourth doped regions 176 b and 177 b are atrespective sides of the switching channel region 131 b 1, and the thirddoped regions 141 b and 142 b are therebetween.

The driving channel region 131 a 1 may have a channel length greaterthan that of the switching channel region 131 b 1. For example, thedriving channel region 131 a 1 may have a long channel length in anarrow space, achieved by a plurality of curved portions. Since thedriving channel region 131 a 1 is long, the driving range of a gatevoltage applied to a first electrode 125 a, which is a driving gateelectrode, widens. Therefore, the gray scale value of light emitted fromthe OLED (e.g., FIG. 2) may be more elaborately controlled and displayquality may improve by changing the gate voltage magnitude.

The first doped regions 141 a and 142 a of the driving semiconductorlayer 131 a and the third doped regions 141 b and 142 b of the switchingsemiconductor layer 131 b may include the same material. The first dopedregions 141 a and 142 a and the third doped regions 141 b and 142 bcorresponding to lightly doped regions may reduce characteristicdeterioration by a hot carrier effect in the driving TFT T1 and theswitching TFT T2, respectively.

The second doped regions 176 a and 177 a of the driving semiconductorlayer 131 a and the fourth doped regions 176 b and 177 b of theswitching semiconductor layer 131 b may include the same material.

A first insulating layer 103 is over substrate 110 and covers thesemiconductor layer 131. The first insulating layer 103 may includemultiple layers, or a single thin layer, including an organic materialand/or an inorganic material including an oxide layer such as SiOxand/or a nitride layer such as SiNx.

A first electrode layer 125 a and a switching gate electrode 125 b areon the first insulating layer 103. The first electrode layer 125 aserves as a driving gate electrode. The switching gate electrode 125 bcorresponds to a portion of the scan line 122.

The storage capacitor Cst includes the first electrode layer 125 a and asecond electrode layer 152 which overlap each, and with a secondinsulating layer 105 therebetween. The first electrode layer 125 aserves as a plate of the storage capacitor Cst and the driving gateelectrode simultaneously. The second insulating layer 105 serves as adielectric, and a storage capacitance is determined based on chargeaccumulated in the storage capacitor and a voltage between the first andsecond electrode layers 125 a and 152. The second insulating layer 105may include multiple layers, or a thin layer of a single layer,including an organic material and/or an inorganic material including anoxide layer such as SiOx and/or a nitride layer such as SiNx.

A storage capacitance may be secured, even in high resolution, byallowing the storage capacitor Cst to overlap the driving semiconductorlayer 131 a in order to secure a region of the storage capacitor Cst,reduced by the driving semiconductor layer 131 a having the curvedportions.

A third insulating layer 107 and a fourth insulating layer 109 cover thestorage capacitor Cst. The data line 171 and the driving voltage line172, etc., may be between the third and fourth insulating layers 107 and109.

A pixel electrode 210 is on the fourth insulating layer 109. Apixel-defining layer covers the edge of the pixel electrode 210, exposesthe upper surface of the pixel electrode 210, and is over the fourthinsulating layer 109. An organic emission layer 220 is on the exposedpixel electrode 210. An opposite electrode 230 is on the organicemission layer 220. The pixel electrode 210 is a reflective electrodeincluding metal. The opposite electrode 230 is a transparent conductiveoxide (TCO) such as indium tin oxide (ITO), or a (semi) transparentelectrode including a thin film metal including Ag and Mg. For example,the pixel electrode 210 is an anode and the opposite electrode 230 maybe a cathode.

The organic emission layer 220 may include a low molecular or polymerorganic material. The organic emission layer 220 includes an emissionlayer and may further include at least one of a hole injection layer(HIL), a hole transport layer (HTL), an electron transport layer (ETL),or an electron injection layer (EIL).

FIG. 5 illustrates an embodiment of a portion V in FIG. 3, along withdriving TFT T1 and the switching TFT T2 in an organic light-emittingdisplay device. Referring to FIG. 5, the driving semiconductor layer 131a of the driving TFT T1 includes the driving channel region 131 a 1having a plurality of curved portions 131 ap, the lightly doped firstdoped regions 141 a and 142 a, and the heavily doped second dopedregions 176 a and 177 a. The heavily doped second doped regions 176 aand 177 a correspond to the source region and the drain region.

The first electrode layer 125 a overlaps only the driving channel region131 a 1 of the driving semiconductor layer 131 a. The first electrodelayer 125 a does not overlap the first and second doped regions 141 a,142 a, 176 a, and 177 a of the driving semiconductor layer 131 a. Sincethe first electrode layer 125 a serves as the plate of the storagecapacitor as well as the driving gate electrode as described above, thefirst electrode layer 125 a may have a polygonal shape with an areagreater than the area of the driving channel region 131 a 1 in order tosecure a storage capacitance. The first electrode layer 125 a has apolygonal shape including a convex portion 125 ac adjacent to the firstdoped regions 141 a and 142 a.

The convex portion 125 ac of the first electrode layer 125 a covers anend of the driving channel region 131 a 1 and is adjacent to the firstdoped regions 141 a and 142 a. The first electrode layer 125 a has theconvex portion 125 ac extending toward the first doped regions 141 a and142 a, and concave portions 125 ae (which are relatively concave)arranged at sides of the convex portion 125 ac. Therefore, one lateralsurface of the first electrode layer 125 a (e.g., a lateral surfaceadjacent to each of the first doped regions 141 a and 142 a) hasunevenness.

A first width W1 of the convex portion 125 ac may be equal to or greaterthan a width W0 of the end of the driving channel region 131 a 1. Thefirst width W1 may also be less than a second width W2 of the firstelectrode layer 125 a in the width direction of the convex portion 125ac. The second width W2 may correspond, for example, to an imaginaryline passing through a point hp (referred to as a half point). The pointhp may be at a location that corresponds, for example, to about themidpoint of the channel length of the driving channel region 131 a 1.

The width direction of the convex portion 125 ac may correspond to adirection perpendicular to a length direction LD of the driving channelregion 131 a 1 in the end of the driving channel region 131 a 1. Sincethe length direction LD of the driving channel region 131 a 1 in the endof the driving channel region 131 a 1 is an X-direction in FIG. 5, thewidth direction of the convex portion 125 ac corresponds to aY-direction.

The switching semiconductor layer 131 b of the switching TFT T2 includesswitching channel region 131 b 1, lightly-doped third regions 141 b and142 b, and heavily doped fourth regions 176 b and 177 b corresponding tothe source and drain regions.

The switching gate electrode 125 b is a portion of the scan line 121,overlaps the switching channel region 131 b 1, and does not overlap thethird and fourth doped regions 141 b, 142 b, 176 b, and 177 b.

As described above, the driving TFT T1 and the switching TFT T2including lightly-doped regions may be formed by a process correspondingto the first electrode layer 125 a and the switching gate electrode 125b.

FIG. 6 illustrates an embodiment of a process for manufacturing adriving thin film transistor and a switching thin film transistor. Forexample, in FIG. 6A, the driving semiconductor layer 131 a and theswitching semiconductor layer 131 b are formed, the first insulatinglayer 103 is formed, and then a metallic layer is formed over the entiresurface of substrate 110. Subsequently, a photoresist with aphotosensitive characteristic is formed over the metallic layer. Next,first and second photoresist patterns 11 and 12 are formed by arranginga photo mask including a desired pattern and exposing and developing thephoto mask. First and second metallic layers 125 a′ and 125 b′ areformed by patterning the metallic layer using the first and secondphotoresist patterns 11 and 12 as a mask. The source and drain regions176 a, 177 a, 176 b, and 177 b are formed by doping with highconcentration impurities using first and second metallic layers 125 a′and 125 b′ as a mask.

Next, as illustrated in FIG. 6B, the first and second photoresistpatterns 11 and 12 are ashed. The first electrode layer 125 a and theswitching gate electrode 125 b are formed by etching a portion of thefirst and second metallic layers 125 a′ and 125 b′ exposed via the firstand second photoresist patterns 13 and 14 after the ashing operation. Bythis etching, only the area of the first electrode layer 125 a isreduced to the same shape as the first metallic layer 125 a′. Only thearea of the switching gate electrode 125 b is reduced to the same shapeas the second metallic layer 125 b′.

Referring to FIG. 6C, the first and third doped regions 141 a, 142 a,141 b, and 142 b are formed by removing the first and second photoresistpatterns 13 and 14 after the ashing and doping with low concentrationimpurities using the first metallic layer 125 a and the switching gateelectrode 125 b as a mask.

Referring to the above-described process, the length of the first dopedregions 141 a and 142 a, which are lightly doped regions, is determinedbased on the difference between the width of the first metallic layer125 a′ and the width of the first metallic layer 125 a. The differencebetween the width of the first metallic layer 125 a′ and the width ofthe first metallic layer 125 a is determined based on a reduction amountΔd1 between the width of the first photoresist pattern 13 before ashingand the width of the first photoresist pattern 13 after ashing.

The length of the third doped regions 141 b and 142 b, which are lightlydoped regions, is determined based on the difference between the widthof the second metallic layer 125 b′ and the width of the switching gateelectrode 125 b. The difference between the width of the second metalliclayer 125 b′ and the width of the switching gate electrode 125 b isdetermined based on a reduction amount Δd2 between the secondphotoresist pattern 12 before ashing and the second photoresist pattern14 after ashing.

The reduction amounts Δd1 and Δd2 in the width of the photoresistpattern according to the ashing process are influenced by a lateraltapered angle of the photoresist pattern. The lateral tapered angle ofthe photoresist pattern is influenced by the area and the shape of alayer below the photoresist pattern.

FIG. 11 illustrates a driving thin film transistor and a switching thinfilm transistor of an organic light-emitting display device according toa comparative example. FIG. 12 illustrates a method for manufacturingthe driving thin film transistor and the switching thin film transistorof FIG. 11.

Referring to FIG. 11, a driving semiconductor layer 1131 a of a drivingTFT TRI includes a driving channel region 1131 a 1, lightly dopedregions 1141 a and 1142 a, and heavily doped regions 1176 a and 1177 a.Unlike the first electrode layer 125 a described with reference to FIG.5, a first electrode layer 1125 a does not include a convex portion.

A switching TFT TR2 includes a switching semiconductor layer 1131 bincluding a switching channel region 1131 b 1, lightly doped regions1141 b and 1142 b, heavily doped regions 1176 b and 1177 b, and aswitching gate electrode 1125 b, which is a portion of the scan line121. The switching TFT TR2 has the same configuration as the switchingTFT T2 described with reference to FIG. 5.

The driving TFT TR1 and the switching TFT TR2 according to thecomparative example are manufactured by the same process as the processfor manufacturing the driving TFT T1 and the switching TFT T2 of theorganic light-emitting display device described with reference to FIGS.6A to 6C.

Referring to FIG. 12A, a metallic layer is formed and first and secondphotoresist patterns PR1 and PR2 are formed over the metallic layer byexposing and developing process. First and second metallic layers 1125a′ and 1125 b′ are formed by patterning the metallic layer using thefirst and second photoresist patterns PR1 and PR2 as a mask.Subsequently, heavily doped regions 1176 a, 1177 a, 1176 b, and 1177 bare formed by doping the driving and switching semiconductor layers 1131a and 1131 b with high concentration impurities using the first andsecond metallic layers 1125 a′ and 1125 b′ as a mask.

Referring to FIG. 12B, the first and second photoresist patterns PR1 andPR2 are ashed. The first electrode layer 1125 a and the switching gateelectrode 1125 b are formed by etching a portion of the first and secondmetallic layers 1125 a′ and 1125 b′ using first and second photoresistpatterns PR3 and PR4 after the ashing operation as a mask. Only the areaof the first electrode layer 1125 a is reduced to the same shape as thefirst metallic layer 1125 a′. Only the area of the second metallic layer1125 b is reduced to the same shape as the second metallic layer 1125 b′by the etching.

Referring to FIG. 12C, lightly doped regions 1141 a, 1142 a, 1141 b, and1142 b are formed by removing the first and second photoresist patternsPR3 and PR4 after ashing, and doping the driving and switchingsemiconductor layers 1131 a and 1131 b with low concentration impuritiesusing the first electrode layer 1125 a and the switching gate electrode1125 b as a mask.

In the above-described manufacturing process, a lateral tapered angle Φ1of the first photoresist pattern PR1 on the first metallic layer 1125 a′having a relatively large area is less than a lateral tapered angle Φ2of the second photoresist pattern PR2 on the second metallic layer 1125b′ having a relatively small area. Since the lateral tapered angle Φ1 ofthe first photoresist pattern PR1 on the first metallic layer 1125 a′ issmall, reduction amounts in the widths of the first and secondphotoresist patterns PR1 and PR2 are different from each other, evenwhen the same ashing process is performed. Thus, the reduction amountΔD1 in the width of the first photoresist pattern PR1 on the firstmetallic layer 1125 a′ is greater than the reduction amount ΔD2 in thewidth of the second photoresist pattern PR2 on the second metallic layer1125 b′. As a result, the length L1 of the lightly doped regions 1141 aand 1142 a of the driving TFT TR1 is greater than the length L2 of thelightly doped regions 1141 b and 1142 b of the switching TFT TR2.

Since the lightly doped regions 1141 b and 1142 b having the long lengthincreases resistance, they influence the characteristic of the drivingTFT TR1 and reduce the resolution of the organic light-emitting displaydevice.

In attempt to resolve this, a method for reducing the area of the firstmetallic layer 1125 a′ has been suggested. However, in this case, thearea of the first electrode layer 1125 a formed by the first metalliclayer 1125 a′ is reduced. Thus, it is difficult to secure a storagecapacitance.

In accordance with one or more embodiments, this problem may be solved.For example, the first electrode layer 125 a is designed to include theconvex portion 125 ac adjacent to the first doped regions 141 a and 142a, which are lightly doped regions.

As described above with reference to FIG. 5, when the first electrodelayer 125 a includes the convex portion 125 ac with the first width W1less than the second width W2, a lateral taper angle (e.g., see FIG. 6)of the first photoresist pattern 11 on the first metallic layer 125 a′(e.g., see FIG. 6) for forming the first electrode layer 125 a isgreater than the lateral taper angle Φ1 (e.g., see FIG. 12) of the firstphotoresist pattern PR1 (e.g., see FIG. 12) according to the comparativeexample.

Therefore, the reduction amount Δd1 (e.g., see FIG. 6) in the width ofthe first photoresist pattern 11 by the ashing operation is less thanthe reduction amount ΔD1 in the width of the first photoresist patternPR1 according to a comparative example. Thus, the length of the firstdoped regions 141 a and 142 a, which are lightly doped regions, of thedriving TFT T1 may be reduced. In this case, the length of the firstdoped regions 141 a and 142 a may be finely adjusted by changing thefirst width W1 of the convex portion 125 ac (W1<W2).

FIGS. 7 and 8 illustrate other embodiments of a driving thin filmtransistor of an organic light-emitting display device. The organiclight-emitting display devices in FIGS. 7 and 8 may be substantially thesame as the organic light-emitting display device in FIG. 5, except thefirst electrode layer 125 a.

Referring to FIGS. 7 and 8, the first electrode layer 125 a may includethe convex portion 125 ac and a second convex portion 125 ad. The firstwidth W1 of the convex portion 125 ac is equal to or greater than thewidth W0 of the end of the driving channel region 131 a 1. The firstwidth W1 of the convex portion 125 ac is also less than the second widthW2 passing through the half point hp of the driving channel region 131 a1 in the width direction (e.g. Y-direction) of the convex portion 125ac.

Like the convex portion 125 ac, the second convex portion 125 ad extendstoward the lengthwise direction (e.g. X-direction) of the drivingchannel region 131 a 1 from the end of the driving channel region 131 a1. In the embodiment of FIG. 7, the second convex portion 125 ad mayextend such that a short side of the second convex portion 125 ad isarranged on the same line as a line on which a short side of the convexportion 125 ac is arranged. In the embodiment of FIG. 8, the secondconvex portion 125 ad may extend such that a short side of the secondconvex portion 125 ad is arranged on a line different from a line onwhich a short side of the convex portion 125 ac is arranged.

The second convex portion 125 ad is spaced apart by a predeterminedinterval from the convex portion 125 ac in the width direction of theconvex portion 125 ac. A concave portion 125 ae (which is relativelyconcave) is between the convex portion 125 ac and the second convexportion 125 ad. The width of the second convex portion 125 ad is in thewidth direction of the convex portion 125 ad and is less than the secondwidth W2. The lateral side of the first electrode layer 125 a adjacentto the first doped regions 141 a and 142 a has unevenness as a result ofthe convex portion 125 ac, second convex portion 125 ad, and concaveportion 125 ae, which is relatively concave.

As illustrated in FIGS. 7 and 8, when the first electrode layer 125 afurther includes the second convex portion 125 ad, storage capacitancemay advantageously be increased. In FIGS. 7 and 8, the second convexportion 125 ad is formed at different sides of the convex portion 125ac. In one embodiment, the second convex portion 125 ad may be formed atonly one side of the convex portion 125 ac.

FIGS. 9 and 10 illustrate other embodiments of a driving thin filmtransistor of an organic light-emitting display device. The embodimentsin FIGS. 9 and 10 are substantially the same as the organiclight-emitting display device in FIG. 5, except the driving channelregion 131 a 1.

Referring to FIGS. 9 and 10, the first electrode layer 125 a includesthe convex portion 125 ac. The first width W1 of the convex portion 125ac is equal to or greater than the width W0 of the end of the drivingchannel region 131 a 1 and less than the second width W2 of the firstelectrode layer 125 ac, which passes through the half point hp of thedriving channel region 131 a 1 in the width direction (e.g. Y-direction)of the convex portion 125 ac.

The driving channel region 131 a 1 may be curved to have, for example,four curved portions 131 ap. For example, as illustrated in FIGS. 9 and10, the curved shape may be an omega (Ω) shape or an alphabet “S” shape.The driving channel region 131 a 1 may have a different curved shape inanother embodiment.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwiseindicated. Accordingly, it will be understood by those of skill in theart that various changes in form and details may be made withoutdeparting from the spirit and scope of the present invention as setforth in the following claims.

What is claimed is:
 1. An organic light-emitting display device,comprising: a switching thin film transistor; a driving thin filmtransistor electrically connected to the switching thin film transistor,the driving thin film transistor including a driving semiconductor layerwhich includes a driving channel region, first doped regions at sides ofthe driving channel region, and second doped regions doped withimpurities of a concentration greater than the first doped regions; astorage capacitor electrically connected to the switching thin filmtransistor and the driving thin film transistor; an organiclight-emitting diode electrically connected to the driving thin filmtransistor; a first insulating layer covering the driving semiconductorlayer; and a first electrode layer over the first insulating layer,wherein the first electrode layer includes convex portions extendingtoward each of the first doped regions and covering an end of thedriving channel region and wherein at least one of the convex portionshas a first width greater than or equal to a width of the end of thedriving channel region.
 2. The organic light-emitting display device asclaimed in claim 1, wherein: the first width is less than a second widthof the first electrode layer in a same width direction as the firstwidth at a point, and the point is a midpoint of a channel length of thedriving channel region.
 3. The organic light-emitting display device asclaimed in claim 1, wherein the driving channel region is curved.
 4. Theorganic light-emitting display device as claimed in claim 3, wherein thedriving semiconductor layer includes a plurality of curved portions. 5.The organic light-emitting display device as claimed in claim 1, furthercomprising: a second insulating layer overlapping the first electrodelayer, a second electrode layer overlapping the first electrode layer,and the second insulating layer is between the first and secondelectrode layers.
 6. The organic light-emitting display device asclaimed in claim 1, wherein the first electrode layer serves as adriving gate electrode of the driving thin film transistor and as aplate of the storage capacitor.
 7. The organic light-emitting displaydevice as claimed in claim 1, wherein: the first electrode layerincludes a second convex portion adjacent to at least one of the convexportions, and the at least one convex portion spaced from the secondconvex portion.
 8. The organic light-emitting display device as claimedin claim 7, wherein the second convex portion extends in a samedirection as an extension direction of the at least one convex portion.9. The organic light-emitting display device as claimed in claim 7,wherein the at least one convex portion is spaced apart from the secondconvex portion in a width direction of the convex portion.
 10. Theorganic light-emitting display device as claimed in claim 1, wherein theswitching thin film transistor includes: a switching channel region,third doped regions at sides of the switching channel region, and fourthdoped regions doped with impurities of a concentration greater than thethird doped regions.
 11. The organic light-emitting display device asclaimed in claim 10, wherein the first doped regions and the third dopedregions include a same material.
 12. The organic light-emitting displaydevice as claimed in claim 10, wherein a length of the switching channelregion is less than a length of the driving channel region.
 13. Theorganic light-emitting display device of claim 1, wherein the firstdoped regions do not overlap the convex portions.
 14. A semiconductordevice, comprising: a first transistor including a semiconductor layer,the semiconductor layer includes first doped regions, a channel regionbetween the first doped regions, and second doped regions doped withimpurities of a greater concentration than the first doped regions; aninsulating layer covering the semiconductor layer; and an electrodelayer over the insulating layer, wherein the electrode layer includesone or more convex portions extending toward the first doped regions,the one or more convex portions covering an end of the channel region,and wherein at least one of the convex portions has a first widthgreater than or equal to a width of the end of the channel region. 15.The semiconductor device as claimed in claim 14, wherein: the firstwidth is less than a second width of the electrode layer in a same widthdirection as the first width at a point, and the point is a midpoint ofa channel length of the channel region.
 16. The semiconductor device asclaimed in claim 14, wherein the channel region is curved.
 17. Thesemiconductor device as claimed in claim 14, wherein the semiconductorlayer includes a plurality of curved portions.
 18. The semiconductordevice as claimed in claim 14, further comprising: a storage capacitorconnected to the transistor, wherein the electrode layer serves as agate electrode of the transistor and a plate of the storage capacitor.